One method of collecting fallen off epithelial cell

Abstract

A person usually falls off epithelial cells as many as 400,000 every day, in which the majority adheres to the internal surface of clothes contacting the skin. So many cells disperse on the collar, sleeve cuff and so on. In order to extract DNA from this kind of forensic samples, the normal method is to cut down the cloth with the fallen cells, then the cloth is digested. Due to the restriction of the cut-down size, only a very small amount of cells are collected by this method. Moreover, also because the existence of the dye, the detergent residuum will inhibit the PCR reactions, the good STR profiles are hardly obtained from a considerable number of these samples. Now a vacuum-collection method was established to collect the fallen cells on the surface of forensic samples in this article. The device was made based on the vacuum cleaner, and a special filter membrane with 5 mm diameter was used. When the device was used to collect cells, the filter membrane was sealed on the inhaling mouth. Then the large area of the forensic can be scanned repeatedly to collect cells. After scanning, the cells were deposited on the external surface of the membrane. The membrane was digested to extract DNA by chelex-100 method [1]. The successful rate of STRs analysis was greatly improved by this method. This method was used in many samples, such as gloves, jacket underwear, shoes, hat, cup and headgear from forensic cases, and the fallen cells were collected from most of them. The satisfied STR profiles were obtained. This vacuum-collection method can collect cells without destroying carriers, and was suitable to the DNA analysis of forensic cases.